leetcode-15-数组题-三数之和

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题目

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解法

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class Solution {
public:

    void changePosAdd(int &pos, vector<int>& nums, int n){
        while((pos + 1 < n) && (nums[pos + 1] == nums[pos]))
            ++pos;
        ++pos;
    }

    void changePosSub(int &pos, vector<int>& nums){
        while((pos - 1 > 0) && (nums[pos - 1] == nums[pos]))
            --pos;
        --pos;
    }

    vector<vector<int>> threeSum(vector<int>& nums) {
        int n = nums.size();
        sort(nums.begin(), nums.end());  // 排序

        vector<vector<int>> results;
        int now = 0;
        while(now < n-2){
            int low = now + 1;
            int high = n - 1;
            while(low < high){
                if(nums[low] + nums[high] == -nums[now]){
                    vector<int> res{nums[now], nums[low], nums[high]};
                    results.push_back(res);
                    changePosAdd(low, nums, n);
                    changePosSub(high, nums);
                }else if(nums[low] + nums[high] > -nums[now]){
                    changePosSub(high, nums);
                }else{
                    changePosAdd(low, nums, n);
                }
            }

            changePosAdd(now, nums, n);
        }

        return results;
    }
}